This invention relates to jigs which separate materials in a feed mixture on the basis of differing specific gravities and especially, but not exclusively, to centrifugal jigs of the general type described in International Patent Publication Nos. WO86/04269 and WO90/00090, in which a feed slurry is introduced into a rotating chamber bounded radially by a screen provided with ragging on its inner surface, the ragging being dilated repetitively to provide jigging action.
In WO86/04269, the ragging is dilated by pulsing the water in a hutch chamber which surrounds the screen. The water is pulsed by means of a diaphragm positioned at the base of the hutch chamber. In WO90/00090, a number of hutch chambers are circumferentially spaced about the jig screen, with the water in the hutch chambers being pulsed sequentially. Each hutch chamber has a diaphragm positioned below the screen, with the diaphragms being actuated by respective pushrods driven by a central crank assembly.
The present invention seeks to provide an improved pulsating mechanism for a jig.
In a first form, the invention provides a centrifugal jig having a container mounted for rotation about a longitudinal axis, the container having an axial region, a peripheral region separated from the axial region by ragging which is radially restrained by screen means, means for introducing feed material to the axial region and means for pulsating fluid in said peripheral region so as to repetitively dilate said ragging, characterised in that the pulsating means is located directly radially outwards of said screen means.
A further form of the invention provides a method of separating components of a feed material on the basis of specific gravity in a container of a centrifugal jig which has an axial region, a peripheral region separated from the axial region by ragging which is radially restrained by screen means, including the steps of rotating the container about its longitudinal axis, introducing the feed material to the axial region and repetitively dilating the ragging by means of pulsating means located directly radially outwards of the screen means.
Preferably, the pulsating means includes a reciprocating wall portion of one or more hutch chambers which comprise the peripheral region, most preferably a portion of a radially outer wall of the hutch chamber, including convergent wall surfaces which lead to the hutch chamber concentrate outlet.
Preferably, the reciprocating wall portion of each hutch chamber reciprocates along a substantially radial line of action which intersects with the screen.
A yet further form of the invention, applicable both to centrifugal and gravity (non-rotary) jigs, provides a jig having at least one hutch chamber, said hutch chamber having a reciprocating wall portion which includes convergent wall surfaces leading to a hutch chamber concentrate outlet.